A projector ( Lat. proiacere "forward throw, throw") is an optical device that is designed to image a surface (canvas) one usually magnified image of an object or image data by computer. Practical applications include the presentation of slides , pictures, graphics or data in presentations , demonstration of computer programs that substitute for a blackboard and film screenings . Projectors for connection to analog and digital signal sources such as computers or video recorders are also video projectors or short Beamer called. Special technical projection applications are in the 3-D optical measurement technology, for example, in the light projection , or the light-section method .
Optical projectors as essential optical elements of a very bright light source and a projection lens , with the help of a person in an appropriate distance projection generates a magnified image of a real, ie physically present smaller image or original.
Exception: imaging solar telescope
By light projectors ( Diaskope ), for example, the slide projector or overhead projector . By light projectors radiate through a medium, like a slide or a printed plastic film or described. Are high-contrast black and white projections of demand, is used instead of a positive film on glass deposited metal masks (see also Gobo ).
From the light source emanating light rays are initially undirected, ie they do not illuminate the medium as a parallel beam. The alignment ( collimation ) of the light rays from the condenser over. The information provided with the image light beam is then passed through a projection lens onto a screen projected . film projectors , enlargers and microfilm readers basically operate similarly. Some video projectors project a transparent liquid crystal display .
Projectors that map the diffusely scattered light of a backscattering object are episcopes . For example, a book page, illuminated and the backscattered light projected on the wall. Episcope are faint and require strong light sources.
Micromirror array (DMD short), often in video projectors are used to use, the reflection of a light beam at small movable mirrors to project images and movies. The mirrors are located on a micro chip and can be individually controlled digitally. Each mirror (pixel) has two positions. In one, he reflects the light to the imaging optics, so that the bright spot appears in the projection. In the other it reflects the light passing to the point of the optics and thus appears dark in the image. With this technique can not only still images but also videos , or the output of a computer screen can be projected.
In laser projection can be generated directly on the screen raster or vector-oriented graphics. It is a non-imaging optical projection. When laser projector to be three in a grid pattern (usually by moving mirror optics ) on the projection surface guided laser beams used the primary colors red, green and blue, which can be individually modulated in brightness.
Using lasers can to light shows projections of individual lines and multiple lines can be generated. While in single lines refractive optics is used (Powell lenses, cylindrical lenses), allow diffractive optical elements in combination with Powell lenses, the projection of multiple lines and matrices.
A carousel or carrousel magazine is used for the continuous operation of a slide projector. In it, all slides in a circle arranged and then fall, depending on the choice before the lenses accordingly (chute principle). Slide change when the slide is pushed back up, the carousel is rotated and the next image before the lens moves.
Another technique is the magazine rack .
The first projector was probably the magic lantern (Latin), "Magic Lantern". It was built in different versions. With one of these designs could be used to create a smooth transition between two images by the projection lamp slowly slid up and down. There are also triple projectors with screens for non-stop change. At the beginning of the 20th Century were offered combined projectors, the transmitted light as well as functioning as a front projector [1] .
At the beginning of photography , it was only possible from photographic plates by contact copy photos to develop and to look at. Later, techniques were developed to the images with a magnification device to produce magnified or when they slide to a wider audience. Thus the way was paved for the small screen, because it was no longer necessary to shoot in the format for the resulting image.
The first small-screen slide comes from Leitz (Wetzlar) and published in 1926, one year after the first miniature camera ( Leica ) was brought to market. This projector (ureja) was the forefather of all the projectors, which later merged with magazine guide, Auto Focus , blending technology and remote viewing of slides allowed. In the course of digitization in the photography, there are now only a few manufacturers of these projectors.
In European cinemas were in the silent projectors from the 1920s Ernemann , Goerz , Zeiss , Gaumont and AEG most widely used. In the cinema of the so-called Abwinkl was very popular, a device which causes the images to some extent from the area on the screen and then fly away from her. A projection equipment that spared the footage particularly in the band not the movie jerks, but continuously went through made ??Ernst Leitz before: the Mechau projector , named after its inventor Emil Mechau . Despite some advantages, he was ultimately too big and too expensive to be able to come out in theaters.
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